A Certificate of Analysis is the single most important document for verifying what is actually in a vial of research peptide. Yet many of the COAs circulating in the research peptide market are, in practice, technically present but not genuinely useful — they report a purity number and a lab name without giving a researcher enough information to catch the failure modes that actually occur in this industry.
This guide breaks down each section of a credible COA, explains what every test measures, and outlines what to check before relying on the document.
What a COA Actually Is
A Certificate of Analysis is an analytical document, issued by a testing laboratory, that records the results of quality control testing performed on a specific manufacturing batch. The key word is specific — a credible COA corresponds to one batch, identified by a batch or lot number, not a generic template reused across every shipment a supplier sends out.
The Two Tests That Matter Most
HPLC: Purity
High-Performance Liquid Chromatography is the standard method for reporting peptide purity. It works by separating the components of a sample and measuring the relative proportion that corresponds to the target peptide versus everything else present — synthesis byproducts, degradation products, or residual salts.
A quality COA includes the actual chromatogram image, not just a percentage figure. When reviewing one, look for a single dominant peak representing the target peptide, the retention time, and minimal noise from minor peaks representing impurities.
For most peptide research applications, ≥98% HPLC purity is the widely accepted standard, though some compounds and applications call for ≥99%.
Mass Spectrometry: Identity
HPLC tells you how pure a sample is — it does not, on its own, confirm that the sample is the correct compound. This is where mass spectrometry matters.
Mass spectrometry works by ionising the peptide and measuring its mass-to-charge ratio, which reveals the molecular weight. A credible COA reports both an observed (or “found”) molecular weight and a calculated (or “expected”) molecular weight for comparison. If these two figures align closely, the compound’s identity is supported.
A COA with HPLC purity but no mass spectrometry data leaves identity unconfirmed. This is one of the more important gaps to check for.
Beyond Purity and Identity
A complete COA for research-grade peptides should also report endotoxin levels (expressed in EU/mg), heavy metals screening (typically mercury, lead, arsenic, and cadmium), and batch-specific identifiers that match the label on the physical vial exactly.
Verifying the Laboratory Itself
A COA is only as credible as the laboratory that produced it. Where possible, check for recognised accreditation markers such as ISO 17025, and consider verifying the testing lab independently — by searching for it yourself and confirming its existence, rather than relying solely on contact details printed on the document itself.
A Practical Checklist
Before relying on a COA, confirm it includes: a batch or lot number matching the physical vial, an HPLC chromatogram image, mass spectrometry data with both observed and calculated molecular weight, a named and independently verifiable testing laboratory, a recent analysis date, and endotoxin and heavy metal results where relevant.
Claripep’s Approach
Every compound listed by Claripep is tested independently by a third-party laboratory before being made available, with the batch-specific COA published alongside the product listing.
This article is provided for research and educational purposes only and does not constitute medical advice. All products supplied by Claripep Ltd are intended strictly for laboratory research applications.